Reconnaissance petrography of the Idaho batholith in Valley County, Idaho

Chlorine Distribution in the Idaho Batholith

“…These indicate that the lead present in the Coeur d'Alene deposits separated from sources of radiogenic lead about 1.4 billion years ago (Zartman, 1971;Long, 1960). This is also the age of the Belt Supergroup metasediments (Kanasewich, 1968) which comprise the material from which the Idaho Batholith might have been formed (Schmidt, 1957;Swanberg, 1973). Kanasewich (1968) suggests that the lead in the Coeur d'Alene district as well as that in other lead-zinc deposits related to the Belt Super-group sediments was originally deposited under conditions similar to those prevailing in the hot brine areas of the modern Red Sea.…”

“…Batholith (Schmidt, 1957). Discussions in this thesis assume that the Idaho Batholith is composite igneous-metamorphic but predominately metamorphic, derived mostly from sedimentary rocks and intruded by usually small igneous stocks (Schmidt, 1957;Swanberg, 1973).…”

“…These intrusions were followed by metasomatism. Schmidt (1957) prefers a primarily metamorphic or metasomatic process, with or without mobilization of the interior portion. It is clear that the margins are metamorphosed and/or metasomatised where exposed.…”

A gravity survey of part of the Long Valley district, Idaho

“…A small part of this gradient can be explained by distant topographic effects. The remaining part of this regional gradient may be caused by the gravity effect of the western border of the Idaho Batholith, or possibly it is the expression of a systematic decrease of density of the outer rock belts ofthe batholith mentioned by Schmidt (1958).…”

Reconnaissance petrographic cross section of the Idaho batholith in Adams and Valley Counties, Idaho

“…1). Most of the material presented here was originally set forth in greater detail in an earlier report (Schmidt, 1958).…”